In many fields of application of commutator motors, in particular with electric tools, such as drills and screwdrivers, the need frequently arises of being able to operate the motor selectively in either direction of rotation. It is well known to use for this purpose reversing switches that reverse the direction of the current flowing through the armature with respect to the current through the field coils, or in the case of a DC motor with a permanent magnet with respect to the magnetic field. The motor is, however, usually switched on and off by means of an additional switch in the power supply, for instance with an electrical hand drill by means of a trigger-switch in the handle. This operation of a portable hand tool is relatively cumbersome because for every reversal in direction of rotation, one must actuate not only the reversing switch but also the trigger-switch. Moreover, there is a risk that the reversal in the direction of rotation will inadvertently occur while the trigger-stitch, or other main switch, is actuated resulting in the likelihood of damage to the motor and possibly also the reversing switch. To avoid this latter problem, combined switches have been developed that effect a mechanical locking between the reversing switch and the main trigger-switch, see for example German Auslegeschrift No. 26 31 994, however such an arrangement increases the cost of the switch.
It has been proposed to use two switches for operating an electric motor in opposite directions of rotation, particularly DC motors. U.S. Pat. No. 3,243,680 discloses such a switching arrangement for opening and closing power operated windows of automobiles, and German Utillty Model Publication No. 1,884,374 discloses a two push button arrangement for operating a zoom lens of a cine-camera.